The present invention generally relates to magnetic disk devices such as hard disk drives, and particularly to a technique of writing servo signals for positioning magnetic heads on magnetic disks.
As one of servo write methods, there is known the self servo-write method for recording servo track information in a magnetic disk device by controlling the magnetic head (hereafter, simply referred to as head) and actuator of a product itself without using any external writing device. This method is concretely disclosed in Japanese Patent No. 2921604 (W096/28814) and JP-A-8-255448.
In the former, reference information for positioning a head, i.e., a servo signal, is written after a head is pressed against a stopper, and the amount of head-feeding, or pitch for positioning is calculated while being adjusted according to the amplitude of its reproduced waveform.
In the latter, the magnetic head is moved by using an external writing device within a clean room so that servo information as a reference can be previously recorded on a part of a magnetic disk (hereafter, simply referred to as disk), and the amount of head-feeding, or pitch for positioning is calculated by reading the recorded pattern.
In the former, however, the regions over which information is written on the disk cannot be fixed, or determined because the head's core width varies, i.e., because very small read and write elements have their tolerances of mounting or size.
Moreover, in order to execute the latter, it is necessary to record a servo signal on part of the disk by using an external writing device. Thus, the latter has the drawback that it spoils the advantage of the self servo-write that does not need any external writing device. In addition, it requires a clean room as a large-scale facility.